I don't think that many drops exist. Here were Bradford's 2015 stats via
NFL.com:
Overall QB: 18th
Passing yards: 18th
Passing Attempts: 12th
Completion percentage: 24th
Average yards per completion: 36th
Average passing yards per game: 15th
TD passes: 23rd
INT: 7th
# of passes 20+ yards: 20th
Season average QB Rating: 38th
So with above average levels of attempts, he was still below average (mostly well below) in pretty much every statistical category except for INT where you are correct he is knocking on the door of being in the NFL top 5. And now that PFM has retired he definitely has the wind at his back to break into that elite category of INT throwers.